1958 TECHNICAL SERVICE MANUAL: V-8 ENGINE
V-8 Engine AssemblyThe V-8 engines are of the same basic design. Therefore, reference is made to the 20-series (250-cid) or 80-Series (327-cid) where parts specifications or procedures apply only to that particular Series. ENGINE IDENTIFICATION The engine number is stamped on the front upper right corner of the cylinder block. Letter Identification, Size of Bore, Main Bearings and Connecting Rod Bearings In the machining of cylinder blocks and crankshafts, it is sometimes necessary to machine the cylinder bores to 0.010" oversize, and the crankshaft main bearing journals or crank pins to 0.010" undersize.
These engines are marked with a three-letter code. The code is stamped adjacent to the engine number. The letters are decoded as follows:
The cylinder block surface has two locating dowels to assist in lining up and holding position of cylinder head and gasket during installation or removal.
Coat the gasket with non-hardening gasket paste. The "A.M." and "TOP" markings on the gasket are located to the top when installing. After installing the push rods, rocker arm assembly, and cylinder head cap screws, tighten them evenly. Then retighten to 60-65 foot pounds with torque wrench following the sequence outlined in Figure 1.
Figure 1 - Torque Tightening Sequence
Fifteen cap screws retain the cylinder head and rocker arm assembly to the cylinder block on each bank. They are of various lengths and design. Four medium 3-15/16", two short 3", two with special tapped heads to accommodate the retaining screws that hold the cylinder head cover 4-1/4", three long plain cap screws to retain rocker arm assembly and cylinder head 6-3/8" long, and one special bolt to index with oil holes for rocker arm lubrication and retain rocker arm shaft and cylinder head 6-3/8" long. This special drilled bolt is part of the lubrication system and must be installed in the rear position to index with oil passages in the tappet area.ROCKER ARM AND SHAFT ASSEMBLY The rocker arm shaft assembly is secured to the cylinder head with four long cylinder head and rocker arm shaft retaining cap screws 6-3/8". The rocker arm shafts are hollow, plugged at each end, serving as oil galleries for rocker arm, push rod end, and valve stem lubrication.
The oil pressure supply for each rocker arm assembly is taken from the valve tappet main oil gallery. The oil under pressure through connecting passages in cylinder block and cylinder head enters through the special drilled rear bolt around the undercut stem area of the rear rocker arm shaft mounting cap screw up- ward into the rocker arm shaft.
Two different rocker arms are used to accommodate the angle from the rocker arm shaft support to the valve stems. However, the rocker arm shaft assemblies are interchangeable from cylinder bank to cylinder bank (Fig. 2).
The rocker arm shafts are 0.858"-0.8585" outside diameter and the rocker arms are 0.860"-0.861" inside diameter. Oil clearance is 0.002".
Figure 2 - Valve Rocker Arm AssemblyValves
Figure 3 - Valve Arrangement
Valve Adjustment 20-Series (250-cid)Hexagon head adjustment screws at the rocker arm provide for valve lash adjustment of 0.012" intake and 0.014" exhaust with engine at normal operating temperature. Check adjustment every 8,000 to 10,000 miles. Valve Adjustment 80-Series (327-cid) Hydraulic valve lifters, no mechanical adjustment is required. Valve Springs Whenever valve springs are removed, they should be tested according to the specifications listed below. Use Valve spring tester and replace all springs not within specifications.
Valve Closed -------- 85-91 Lbs. @ 1-13/16"
Valve Open --------- 150-160 Lbs. @ 1-7/16"
Valve springs are installed with the inactive (closed) coils against the cylinder head.
The valve spring retainer serves the purpose of holding the valve and spring together. The seal is mounted onto the valve guide. At valve service periods, the valve stem oil seals should be replaced to insure good oil control at this point.
The half-conical shaped valve locks can be removed after compressing the spring.
Valve springs are 2.20" long free length. They are 0.938"-0.953" inside diameter.Valve Stem to Guide Clearance The valve stem to guide clearance is maintained through replacement of valve guides. The valve guides are an interference fit in their bores in the cylinder head and can be replaced by driving out the old guides and driving in the new. The new guides are driven to a depth to permit 3/4" +/- 1/64" to remain exposed above the cylinder head. Measure from top of the guide to flat machined surface for lower valve spring retainer.
New valve stem to guide clearance is as follows:
Figure 4 - Valve, Push Rod and Tappet Assembly - Hydraulic Tappet Illustrated
Valve guides are reamed to 0.3430"-0.3440" inside diameter, after installation.
Rubber valve stem oil deflectors are provided on the valve guides to aid in preventing oil consumption between the valve stem and guide.Valve Refacing The intake valves are faced to a 29° angle and the exhaust valves to a 44° angle. Valves may be refaced until remaining margin is down to 1/32"; then the valve must be replaced.
The valve stem tip when worn can be resurfaced and rechamfered. However, never remove more than 0.010".Valve Seat Refacing Grind the valve seats to the following specifications:
Narrowing stones should be used to obtain the proper seat widths when required. Control seat run-out to a maximum of 0.002".Hydraulic Valve Tappets The hydraulic valve tappet consists of a body, plunger, plunger return spring, check valve assembly, pushrod socket and lock ring (Fig. 5).
Figure 5 - Sectional View of Hydraulic Tappet Assembly
The tappet operates in a guide bore which has an oil passage drilled into the adjoining main oil galleries.
When the tappet is on the heel of the earn lobe, the plunger return spring indexes an oil hole undercut in the plunger with the oil supply admitted through the tappet body. Oil under pressure flows into the body through the check valve assembly maintaining the tappet fully charged. This cycle of operation occurs when tappet leaks off some oil during the normal valve opening events. Opening movement of the cam lobe causes tappet body movement, closing the check valve and transmitting "zero-lash" movement of the push rod to open the cylinder valve.
The valve tappets should be cleaned and serviced at time of engine overhaul or whenever excessive noise exists.
When removing the tappets, they must be kept in an order that will insure replacement in their respective operating bores in the engine because they are select fitted to that bore. Keep each hydraulic tappet component group by itself as all detail components are select fitted to one another in manufacturing. Only complete tappet assemblies are supplied for service replacement.
The hydraulic tappet assembly should be cleaned in a solvent to remove all varnish or leaded deposits. After cleaning, the tappet must be "leak-down" tested to insure its "zero-lash" operating ability. Kerosene should be used for this test.Figure 6 illustrates Tool J-5790 used to accurately test tappet "leak-down." They may also be tested by filling the body with kerosene and then install the plunger return spring, plunger assembly and pushrod socket. Leave out snap ring for test. Insert the push rod in tappet socket and check it for "leak-down" by pushing downward on rod.
Figure 6 - Testing Valve Tappet "Leak Down" with J-5790
If the tappet leaks down rapidly or collapses immediately, it must be rechecked and/or replaced with a complete new tappet assembly. The normal tappet will take approximately 10-45 seconds to "leak-down" with kerosene with a 50-lb. load, travel of 0.125". After testing tappets, they should be pre-lubricated and assembled in the engine without an oil charge. They will normally charge themselves in 3 to 8 minutes of engine operation.Tappet Noise A loud clicking noise is usually the result of the plunger stuck down below its operating position or a check valve held open. A light clicking noise is usually the result of excessive "leak-down" caused by wear or slight leakage at the check valve and its seat.
An intermittent noise at tappet is the result of dirt or chips stopping the check valve or a lack of oil flow into the body because of dirt. A general tappet noise is in most cases due to a lack of oil volume or pressure.
The normal tappet plunger operating range is 0.143".Valve Timing The correct valve timing is established by the relation between the sprocket on the camshaft and the sprocket on the crankshaft.
To obtain the correct valve timing, index the "O" marks on camshaft and crankshaft sprockets on a line drawn vertically through the centerline of each shaft (Fig. 7). To check the assembly, rotate the crankshaft until the timing mark on camshaft sprocket is on a horizontal line at either the 3 or 9 O'clock position. Count the number of links or pins on the timing chain between timing marks. You should have 10 links and/or 20 pins between timing marks. Each link contains two pins (Fig. 8).
Figure 7 - Properly Installed Timing Assembly
Figure 8 - Link Count Position
To make an external check of valve timing, remove the cylinder head covers and spark plugs. Crank the engine until No. 6 cylinder piston in the Right Bank is on TDC on compression stroke. This places No. 1 cylinder piston on TDC on the exhaust stroke valve overlap position. Rotate the crankshaft counterclockwise 90° .
Install a dial indicator on the number one intake valve rocker arm push rod end (Fig. 9). Crank the engine slowly in direction of rotation (clockwise) until the dial indicator indicates push rod movement. The hydraulic lifter should be fully charged for this check.At the time the dial indicator moves the ignition-timing pointer on the front cover should align with a point approximately 25/32" before TDC position on the vibration damper. If more than 1/2" variance in either direction is evident, remove the timing chain cover and inspect timing chain installation. Replace timing chain if over 1/2" of chain deflection exists.
Figure 9 - Installation of Dial Indicator for External Valve Timing Check
Figure 10 - Valve Timing Diagram - Hydraulic Actuated Valves
Figure 11 - Valve Timing Diagram - Mechanically Actuated Valves TIMING CHAIN COVER The timing chain cover is a casting incorporating an oil seal at the vibration damper hub.
To remove the timing chain cover, first remove water pump, fuel pump assembly, and vibration damper.
Figure 12 - Timing Chain Cover
To prevent damage to the oil seal, it is important that the cover be property aligned when installing the vibration damper. This is accomplished by locating dowels in the cylinder block and by leaving the cover to block screws loose until the vibration damper has been partially installed. Then tighten the cover screws.CAMSHAFT AND BEARINGS The camshaft is supported by five steel-shelled, babitt-lined bearings which have been pressed into the block and line reamed. The camshaft bearings are step bored, being larger at the front bearing than at the rear, to permit easy removal and installation of the camshaft. All camshaft bearings are lubricated under pressure.
The oil lubrication is supplied through connecting drilled passages from the central main oil gallery.
Camshaft cam heels should not run-out over 0.001" on base circle when gauged between two adjacent camshaft bearings. Camshaft oil clearance is 0.001" to 0.003".Camshaft End Play The camshaft end thrust is controlled by the front surface of the camshaft bearing and the rear surface of the thrust plate, and the rear hub surface of the camshaft sprocket and the front surface of the thrust plate.
The end play tolerance is .003" to .006".Camshaft Removal Remove cylinder head covers, ignition plug wires, rocker arm assemblies, intake manifold, and carburetor. Remove upper oil breather and tappet assembly cover. Remove inner oil baffle cover. Remove push rods, keeping them in their relative operational positions. Remove hydraulic tappets and keep in relative operational positions. Remove fuel pump, vibration damper, and timing chain cover. Remove water pump and cylinder head water distribution manifold. Crank engine until timing marks line up on a vertical line with shaft centers (Fig. 7).
Remove fuel pump eccentric, crankshaft sprocket, camshaft sprocket, and timing chain assembly. Timing sprockets can be pried off with ease.
Remove the camshaft retainer thrust plate and the end thrust spacer (Fig. 13).
Figure 13 - Camshaft Thrust Plate PISTONS Slipper-type, tapered skirt, cam ground pistons are used. They are of aluminum alloy, steel reinforced for controlled expansion. The ring belt area provides for three piston rings, two compression and one oil control ring above the piston pin.
The pistons are removed from the top of cylinder bore after removing ring ridge.
The piston pin boss is "offset" from the piston centerline to place it nearer the thrust side of the cylinder.
To insure proper installation of the piston in the bore, a notch is cast in the piston top, and letters "F" cast in the pin boss structure at the front (Fig. 14).
Figure 14 - Correct Piston Position
The piston to bore clearances are:
PISTON PINSThe piston pins are a press fit into the connecting rod, thus requiring no locking device.
The piston pin is removed with piston pin remover J-6360 and an arbor press. The piston is placed on the remover support so that the pin will enter the support when pressed out with the piloted driver.
To install the piston pin, place the piston pin pilot in the support and insert in piston and connecting rod. This aligns the piston and connecting rod piston pin bores. Press the piston pin into the connecting rod and piston assembly until the lower pilot bottoms in the support. The connecting rod is automatically centered on the pin (Figs. 15 and 16).
CAUTION: The pin must be a tight press fit in the connecting rod.
The piston pin should be a palm press fit in piston boss at room temperature. With parts dry and free of oil, the pin must support its weight in a vertical position, over its entire length, in either of the two piston pin bosses.
Figure 15 - Removing Piston Pin
Figure 16 - Installing Piston Pin PISTON RINGS
A three ring piston is used. The two compression and one oil control rings are located above the piston pin boss.
Before assembling the rings to the piston, carbon must he cleaned from all ring grooves. The oil drain holes in the oil ring grooves and pin boss must he cleared with the proper size drill. Care must be exercised not to remove metal from the grooves since that will change their depth, nor from the lands since that will change the ring groove clearance and destroy ring to land seating.
Figure 17 - Piston Ring Location Checking Ring Groove Clearance Side clearance between land and piston ring should be:
Roll the ring around the groove in which it is to operate. It must fit freely at all points.Checking Ring Gap Clearance Piston ring gap or joint clearance is measured in the bottom of the cylinder near the end of the ring travel area. To square the ring in the bore for checking joint clearance, place the ring in the bore. Then with an inverted piston, push the ring down near the lower end of the ring travel area.
When other than standard ring sizes are used, rings should be individually fitted to their respective bores for a gap clearance of:
Successful ring installation depends upon cleanliness in handling parts and while honing the cylinder walls. The engine bearings and lubrication system must be protected from abrasives.
Rigid type hones are not to be used to remove cylinder glaze as there is always a slight amount of taper in cylinder walls after the engine has been in -service.
Rings must be installed on the pistons with a ring-installing tool to prevent distortion and ring breakage.
Prior to installing the piston and connecting rod assembly into engine, the piston ring gaps are to be arranged so that the gap for the oil ring is toward the inside of the block. The gaps on the compression rings are 120° apart. Do not locate a ring gap over the piston pin boss.Service Piston Ring Sets For service ring replacement, follow detailed instructions enclosed in the ring package. CONNECTING RODS
Connecting rods are the "I" beam drop forged steel type. The connecting rods are stamped with the cylinder numbers in which they are assembled. The numbers are opposite the squirt holes and toward the outside of the banks in which they are located.
The squirt holes from connecting rods in one bank lubricate the cylinders in the opposite bank.
The connecting rod squirt holes are located in the parting surface of the bearing cap (Fig. 18).
Figure 18 - Connecting Rod Squirt Hole Location
Assemble connecting rod to piston with notch in piston and connecting rod identification mark to front of engine. Cylinder numbers should be toward the outside of bank in which they are installed.
Figure 19 - Connecting Rod Identification Mark
The cylinders are numbered 1, 3, 5, 7 in the left bank of engine from front to rear, and even numbers 2, 4, 6, 8 in the right bank, front to rear as viewed from driver's seat.
Two connecting rods are mounted side by side on each crankpin. The side clearance is 0.004" to 0.012" (Fig. 20).
Figure 20 - Checking Connecting Rod Side Clearance
Connecting Rod Alignment
Whenever new rings are installed or new piston pins are replaced, it is necessary to align the connecting rods and pistons as assemblies to insure true operation in the cylinder bore.
Figure 21 - Piston and Connecting Rod Assembly
Misaligned rods will cause uneven piston and ring wear, which will result in oil consumption. The connecting rod should be inspected for a twisted or bent condition.
Connecting Rod Bearings
The connecting rod bearings are the steel-backed, babbitt-lined precision type. They are installed as pairs in the connecting rod and cap.
CAUTION: Never file a connecting rod or cap to adjust bearing clearance.
To determine the amount of bearing clearance, use a piece of Plastigage in the bearing cap. Then tighten the cap to torque specifications to compress the gauge. Remove the bearing cap and calibrate the width of the Plastigage with the scale furnished.
If the bearing clearance is excessive, the correct undersize bearing insert (pair) should be installed in the connecting rod.
The correct connecting rod bearing clearance is 0.0007" to 0.0028".
The crankpin diameter is 2.2483" to 2.2490".
It is important that the connecting rod bearing cap bolt nuts be drawn up to 46-50 foot pounds torque.
Connecting rod bearings are serviced in 0.001", 0.002", 0.010", 0.012" undersize.
The crankshaft is a drop forged steel shaft, counterweighted and balanced independently. There are five main bearings and four crankpins. It is provided with an oil slinger at rear journal inboard of the rear oil seal.
The component parts of the crankshaft assembly are individually balanced, and then the complete assembly is balanced as a unit. Replacement of crankshaft, flywheel, or vibration damper can be accomplished without rebalancing the complete assembly.
Main Bearing Journals
Main bearing journals can be measured without removing the crankshaft from the engine block. Various gauges are available for this purpose. Always check both ends of the journal to note the taper. Then rotate the shaft 90° and measure for out-of-round.
The main bearing diameter is 2.4983" to 2.4990" and should not taper or be out of round more than 0.002".
Crankshaft Main Bearings
Main bearings are of the precision type having a steel back with a babbitt lining. The bearings are not adjustable. Shims should never be used and the bearing caps should never be filed,
Service bearings are supplied in 0.001", 0.002", 0.010", and 0.012" undersize.
When either half of a bearing requires replacement, a complete set should be installed. To replace the upper half of a bearing, remove the bearing cap of the bearing to be replaced. Then loosen all of the other bearing caps and insert a small pin about 1/2" long in the crankshaft oil hole. The head of this pin should be large enough so that it will not fall into the oil hole, yet thinner than the thickness of the bearing.
With the pin in place, rotate the shaft so that the upper half of the bearing will rotate in the direction of the locating tongue on the bearing.
Crankshaft Main Bearing Clearance
The standard clearance of 0.0006" to 0.0032" can be accurately checked by the use of Plastigage.
NOTE: When checking bearing clearance, with the engine in such a position that the bearing caps support the weight of the crankshaft and flywheel, keep all main bearings tight except the one being checked. Support the weight of the crankshaft with a jack.
Remove the bearing cap and wipe the oil from the bearing insert.
Place a piece of Plastigage across the full width of the bearing insert.
Reinstall the bearing cap and tighten 80 to 85 foot pounds torque. Then remove the bearing cap and with the graduated scale, which is printed on the Plastigage envelope, measure the width of the flattened Plastigage at its widest point. The number within the graduation indicates the clearance in thousandths of an inch. Install the proper size bearing liners (inserts) to bring the clearance to standard.
Grinding of the crankshaft may be required to accommodate the nearest undersize bearings when cleaning up a scored bearing surface.Crankshaft End Play The crankshaft end thrust of 0.003" to 0.007" is taken at the front or No. 1 bearing insert, which is flanged for this purpose.
To check this clearance, attach a dial indicator to the crankcase and pry the shaft fore and aft with a screwdriver (Fig. 22).
Figure 22 - Checking Crankshaft End Thrust REAR MAIN BEARING OIL SEALS The rear main bearing oil seal is composed of two hemp packings, one in the block, the other in the cap. (Fig. 23).
Figure 23 - Main Bearing Arrangement
The packing is driven into place with Tool J-3048-A (Fig. 24). Excess packing is cut off flush with the cap.
Figure 24 - Installing Hemp Packing Oil Seal in Rear Main Bearing Cap VIBRATION DAMPER The vibration damper is balanced independently and then rebalanced as part of the complete crankshaft assembly.
Service replacement dampers may be installed without attempt to duplicate balance holes present in original damper.
Figure 25 illustrates a vibration damper puller, which may be fabricated locally.
Figure 25 - Suggested Damper Puller
In the event of engine noises, it is timesaving to inspect the vibration damper assembly before engine teardown. Incorrect assembly of the cushions and rubbers will permit a noise similar to bearing noises.
Engine support cushions also are a source of misdiagnosed engine bearing rap.
Figure 26 - Vibration Dampner Pulley (1) Pulley (2) Rubber Cushion (3) Rubber Friction Washer (4) Hub (5) Friction Disc FLYWHEEL AND STARTER RING GEAR ASSEMBLY With the exception of the ring gear used with the automatic transmission, which, is welded to and balanced as part of the torque converter assembly, the starter ring gear can be replaced by placing the flywheel in an arbor press with steel blocks equally spaced around the gear and pressing the flywheel through, or the ring gear can be broken with a chisel.
To install the new starter ring gear, first heat it to expand the inside diameter so that it can be pressed over the flywheel.
On standard and overdrive transmission equipped cars- the flywheel is balanced as an individual component and also as part of the crankshaft assembly.
Service replacement flywheels may be installed without attempt to duplicate balance holes present in original assembly.LUBRICATION SYSTEM The lubrication system is the full pressure type. Pressure is supplied by a gear type, positive pressure pump mounted on the rear main bearing cap. Oil Pump The oil pump is driven by the distributor drive shaft. Oil pump removal or replacement will not affect distributor timing, as the distributor drive gear remains in mesh with the camshaft gear.
Upon disassembly of the oil pump, locate a straight edge across the pump body and gears in their operational cavity and check the gear to cover clearance, which should not exceed 0.004".
A clearance of 0.008" maximum should exist between the gears and the walls of the gear cavity opposite point of gear mesh.
NOTE: The pump cover should be installed with pump out of engine and pump checked for freedom of operation before installation.Figure 27 - Oil Pump Assembly Oil Pressure Relief Valve The oil pressure relief valve is not adjustable. A setting of 55-60 pounds pressure is built into the tension of the spring.
On the released position, the valve permits oil to by-pass through ports and a passage in the pump cover to the inlet side of the pump.Lubrication Circuit Oil drawn through the inlet screen and tube assembly is displaced into the pressure discharge side of pump to a port indexing with a vertical oil gallery up into the cylinder block where it indexes with a horizontal passage leading to the lower oil filter mounting adapter (Fig. 29).
Oil is returned from the oil filter to the main central longitudinal oil gallery. All camshaft and main crankshaft bearings are lubricated from the center longitudinal oil gallery. Holes drilled in the crankshaft throws afford lubrication to the connecting rod bearings. Low speed cylinder wall lubrication is obtained through small holes or channels in the parting surface of the connecting rod and bearing caps.
Throw-off oil from the connecting rods lubricates camshaft lobes and cylinder walls at higher speeds.
Passages at the front of the engine (Fig. 28) and in the camshaft thrust plate (Fig. 13) connect the main center oil gallery with the two (left and right) oil galleries to the hydraulic valve tappets.
Figure 28 - Cylinder Block Oil Passages
At the rear section of each tappet oil gallery (Fig. 28), a passage connects upward to the rear rocker arm shaft support retaining bolthole. These bolts are drilled to permit oil flow to the rocker arm shafts, rocker arms, push rods, valve stems, and valve guides.
Two drain holes in the lower corners of the cylinder head casting return the oil to the oil pan.
Figure 29 - Cylinder Block Oil Passages Oil Filter A full flow oil filter mounted on the lower rear left hand side of the engine is accessible from below the car.
A bypass valve is incorporated in the filter to provide a safety factor in the event the filter becomes inoperative as a result of dirt or sludge accumulation.
Normally, no tools are required to replace the filter at recommended four thousand (4000) mile intervals.
The discard type filter unit is removed from the adapter by hand. The replacement unit is turned on until the gasket contacts the seat and then tightened an additional half turn.
One additional quart of oil is required when a filter unit is replaced.
Figure 30 - Full Flow Oil Filter
PISTONS AND RINGS
CRANKSHAFT AND BEARINGS